Q: How many atoms are in $1.25$ moles of cobalt?

$1.25 \times 6.022 \times 10^{23} = 7.53 \times 10^{23}$ atoms

Q: What is the molar mass of $\mathrm{CO}_2$?

$12.01\ \mathrm{g/mol} + 2 \times 16.00\ \mathrm{g/mol} = 44.01\ \mathrm{g/mol}$

Q: How many molecules are in $0.82$ moles of a compound?

$0.82 \times 6.022 \times 10^{23} = 4.94 \times 10^{23}$ molecules

Q: A sample of octane ($\mathrm{C}_8\mathrm{H}_{18}$) contains $8.28 \times 10^{24}$ atoms of hydrogen. How many moles of octane does this sample contain?

$\frac{8.28 \times 10^{24}}{18 \times 6.022 \times 10^{23}} = 0.76$ moles

Question 1

Which of the following statements best describes the difference between accuracy and precision in scientific measurements?

Accepted Answer

Accuracy is how close measurements are to the true value, while precision is how reproducible measurements are to each other.

Question 2

A sample of liquid has a mass of 29.2 g and a volume of 25.5 mL. What is its density?

Accepted Answer

$d = \frac{29.2}{25.5} = 1.15\ \mathrm{g/mL}$

Question 3

Convert 0.000538 to scientific notation.

Accepted Answer

$5.38 	imes 10^{-4}$

Question 4

A cup contains 240 mL of water. How many liters is this?

Accepted Answer

$0.24\ \mathrm{L}$

Question 5

Which metric prefix represents $10^{-6}$?

Accepted Answer

micro

Question 6

A fever has a temperature of $104^{\circ}\mathrm{F}$. What is this temperature in Celsius?

Accepted Answer

$45^{\circ}\mathrm{C}$

Question 7

How many atoms are in $1.25$ moles of cobalt?

Accepted Answer

$1.25 	imes 6.022 	imes 10^{23} = 7.53 	imes 10^{23}$ atoms

Question 8

What is the correct scientific notation for 7,934?

Accepted Answer

$7.934 	imes 10^{3}$

Question 9

A piece of salmon contains 15% omega-3 fatty acids by mass. What is the equality and conversion factor for this statement?

Accepted Answer

Equality: $15\ \mathrm{g}$ omega-3 fatty acids $= 100\ \mathrm{g}$ salmon; Conversion factor: $\frac{15\ \mathrm{g}\ 	ext{omega-3}}{100\ \mathrm{g}\ 	ext{salmon}}$

Question 10

What is the molar mass of $\mathrm{CO}_2$?

Accepted Answer

$12.01\ \mathrm{g/mol} + 2 	imes 16.00\ \mathrm{g/mol} = 44.01\ \mathrm{g/mol}$

Question 11

How many moles of water are present in $200\ \mathrm{g}$ of water? (Molar mass of water $= 18.02\ \mathrm{g/mol}$)

Accepted Answer

$\frac{200}{18.02} = 11.1$ moles

Question 12

A sample of calcium chloride ($\mathrm{CaCl}_2$) contains $8.25\ \mathrm{g}$. What is the number of moles present? (Molar mass of $\mathrm{CaCl}_2 = 110.98\ \mathrm{g/mol}$)

Accepted Answer

$\frac{8.25}{110.98} = 0.074$ moles

Question 13

Which of the following is the correct conversion factor to convert kilometers to meters?

Accepted Answer

$\frac{1000\ \mathrm{m}}{1\ \mathrm{km}}$

Question 14

A compound has the formula $\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6$. How many moles of hydrogen atoms are present in $0.50$ moles of the compound?

Accepted Answer

$0.50 	imes 12 = 6.0$ moles$

Question 15

Which of the following is the correct formula to convert Celsius to Kelvin?

Accepted Answer

$T_K = T_C + 273$

Question 16

How many molecules are in $0.82$ moles of a compound?

Accepted Answer

$0.82 	imes 6.022 	imes 10^{23} = 4.94 	imes 10^{23}$ molecules

Question 17

A sample of octane ($\mathrm{C}_8\mathrm{H}_{18}$) contains $8.28 	imes 10^{24}$ atoms of hydrogen. How many moles of octane does this sample contain?

Accepted Answer

$\frac{8.28 	imes 10^{24}}{18 	imes 6.022 	imes 10^{23}} = 0.76$ moles

Matter and Measurements: Mathematical Concepts, Scientific Notation, and Metric Conversions

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